<template>
  <div :class="{ mycolor: isTrue }"></div>
</template>

<script>
import { ref } from "vue";

export default {
  setup() {
    let isTrue = ref(true);
    return {
      isTrue,
    };
  },
};
</script>

<style scoped>
.mycolor {
  width: 200px;
  height: 200px;
  background-color: red;
}
</style>